The object of the present invention is a removable insertion canister located in a transportation and/or storage container, the canister having shafts for radioactive material, particularly for receiving spent fuel elements from nuclear reactors.
There is normally required an insertion canister in transportation and/or storage containers, in order to simultaneously dispose of several spent fuel elements from nuclear reactors during transportation or also during the storage to dispose them in predetermined distance from each other in a container. Therefore, the fuel elements positions corresponding necessary are constructed as correspondingly shafts into which the fuel elements are inserted. The cross-section of the shaft is adjusted in form and dimensions according to the type of fuel element inserted. Besides the fuel elements must be able to be inserted and removed without trouble by remote control. The insertion canister must be sufficiently stable in order that it can withstand the mechanical and thermal loadings during transportation. Besides it must be so constructed that the fuel elements transported are not damaged during the transportation and handling.
Such insertion canisters are normally constructed as pure steel frameworks or as massive blocks of non-ferrous metal. The shafts of the massive blocks are produced by machines. In a given case they are steel-clad.
Steel frameworks are suited as insertion canisters if a corresponding liquid is located in the transportation and/or storage container and which leads off the residual heat produced on the container wall by the fuel elements. The steel framework can consist of boron steel in which boron serves as a neutron absorber.
The massive non-ferrous metal constructions provided with shafts are suited as insertion canister since they make possible the drawing off of the residual heat produced without a helping medium on the container wall. They preferably consist of aluminum or copper or their alloys. These alloys in a given case can have added thereto boron or cadmium as neutron absorbers.
The previously known insertion canisters have a series of disadvantages. They have a high weight since they are constructed predominantly of metal because of the thermal conductivity required. Partially, particularly with special steel frameworks, there is necessary a disadvantageous water cooling in case of accident. The neutron shielding only takes place to a slight extent through the canister, the chief shielding effect is guaranteed through a separate neutron protection on the shielding transportation or stroage container. In the case of accidents, e.g. also fire, this neutron protection on the shielding container however, is destroyed.
Therefore it was the problem of the present invention to provide a removable insertion canister located in a transportation and/or storage container, the canister having shafts for radioactive material, especially for receiving spent fuel elements from nuclear reactors, which have a low weight, an effective neutron shielding and sufficient heat conductivity as well as being usable as an independent intermediate or final storage container.